TW201529483A - Method for treating an acidic waste solution - Google Patents

Abstract

The present invention provides a method for treating an acidic waste solution comprising the steps of: providing an acidic waste solution; filtering the acidic waste solution to remove impurities from the acidic waste solution; adding an alkaline solution into the acidic waste solution to produce solid fluorosilicates; separating the solid fluorosilicates from the acidic waste solution; adding the first buffer agent into the acidic waste solution, so that the pH value of the acidic waste solution is adjusted to the first pH value; exchanging cationic impurities of the acidic waste solution with cations in a cation-exchange resin; adding the second buffer agent into the acidic waste solution, so that the first pH value of the acidic waste solution is adjusted to the second pH value and the reaction between the acidic waste solution and the buffer agent produces fluorides and an aqueous solution ; separating the fluorides from the aqueous solution to obtain the solid fluorides.

Description

Waste acid solution treatment method

The present invention relates to a method for treating a spent acid solution, and more particularly to a method for treating a spent acid solution produced by etching an etching solution of a germanium wafer or glass.

In recent years, the semiconductor industry and the optoelectronic manufacturing industry have flourished, and the types and quantities of wastewater generated during the manufacturing process have increased, such as in the electronics industry, wafer cleaning or etching processes, or etching in planar display (TFT-LCD) processes. The hydrofluoric acid-containing waste liquid produced on the glass substrate cannot be reused because it contains hydrofluoric acid and contains or does not contain impurities such as cesium, nitric acid, hydrochloric acid or sulfuric acid, and must be treated as waste water. However, these wastewaters generally contain impurities such as hydrofluoric acid, nitric acid, hydrochloric acid, and dissolved cesium. When treated as wastewater, a large amount of alkali must be used for neutralization treatment, and the addition of calcium salts to remove fluorine produces a lot of fine fluorine-containing sludge. It is very difficult to handle and requires considerable expense. In addition, it is impossible to recover the fluorine content in order to obtain industrially usable products, and it can only be treated as sludge, which is a waste of resources.

Therefore, how to treat these waste liquids as wastewater treatment and recycle valuable fluorine resources for use in other industries is a problem worthy of expectation and development. The methods that are commonly used at present, including Calcium hydroxide (Ca(OH)2) or calcium chloride (CaCl2) is added to the waste liquid to cause fluoride ion (F-) and calcium ion (Ca2+) to form a calcium fluoride precipitate which is hardly soluble in water. Since the waste liquid contains impurities such as dissolved cerium oxide and sulfuric acid, the resulting calcium fluoride precipitate has a coprecipitate of cerium oxide, sulfuric acid and calcium, so that only low purity calcium fluoride can be obtained. It cannot be supplied for industrial use and can only be treated as sludge, and the economic value that can be created is not high.

In addition, the calcium fluoride precipitate is very fine, the sedimentation rate is very slow, the filtration is very difficult, and the processing equipment requires a large space, so the relative investment cost is quite large, so the treatment contains hydrofluoric acid and contains or does not contain dissolved hydrazine, The treatment of waste acid such as nitric acid, hydrochloric acid or sulfuric acid requires an economical and low treatment cost waste acid recovery treatment to improve the current problems.

The main object of the present invention is to disclose a method for treating a spent acid solution after etching a germanium wafer or glass, and reacting the alkaline solution with a spent acid solution to produce a fluorine-containing strontium salt, and then using a buffer to adjust the spent acid solution. The pH value causes the fluoride ion in the spent acid solution to react with the buffer to obtain a high-priced and high-purity fluoride, which can be used in other industries.

Another object of the present invention is to recover valuable and highly pure fluoroantimonate and fluoride from a spent acid solution by a two-stage treatment procedure in a spent acid solution after etching a wafer or glass.

According to the above object, the present invention discloses a waste acid solution treatment The method comprises: providing a waste acid solution; performing a filtration step, filtering the waste acid solution to remove impurities in the waste acid solution; adding an alkaline solution to the waste acid solution to produce a fluorine-containing citrate solid; The solid-liquid separation step separates the fluorine-containing citrate solids from the spent acid solution; adjusts the pH value of the waste acid solution by adding the first buffer to the spent acid solution to make the pH value of the spent acid solution Adjusting to the first pH value; performing a cation exchange treatment, replacing the cation impurities of the spent acid solution with the cations in the cation exchange resin; adjusting the first pH value of the waste acid solution to the second pH value, The second buffer is added to the spent acid solution, so that the pH value of the spent acid solution is adjusted from the first pH value to the second pH value, and the spent acid solution reacts with the buffer to generate fluoride and an aqueous solution; and the second solid The liquid separation step separates the fluoride from the aqueous solution to obtain a solid fluoride.

In an embodiment of the invention, the waste acid solution includes hydrofluoric acid, fluoroantimonic acid, sulfuric acid, nitric acid, hydrochloric acid or the like.

In an embodiment of the invention, the alkaline solution is a sodium hydroxide solution, and the concentration ranges from 10% to 60%.

In one embodiment of the invention, the first solid-liquid separation step includes a centrifugation step, a dehydration step, and a drying step.

In one embodiment of the present invention, the first buffer is a sodium hydroxide solution having a concentration ranging from 10% to 60%.

In one embodiment of the present invention, the first acid-base value of the above-mentioned spent acid solution is 2 to 4.

In one embodiment of the invention, the cation exchange treatment described above utilizes a sodium-type (Na-type) cation exchange resin.

In one embodiment of the present invention, the second buffer is a sodium hydroxide solution having a concentration ranging from 10% to 60%.

In an embodiment of the invention, the second acid-base value of the waste acid solution is 8-10.

In an embodiment of the invention, the second solid-liquid separation step comprises a centrifugation step, a dehydration step and a drying step.

The above and other objects and advantages of the present invention will be readily understood from

Of course, the invention may be varied on certain components, or in the arrangement of the components, but the selected embodiments are described in detail in the specification and their construction is shown in the drawings.

Step 11‧‧‧ Provide waste acid solution

Step 13‧‧‧Filter the spent acid solution

Step 15‧‧‧ Add an alkaline solution to the spent acid solution to produce a fluorocitrate solid

Step 17‧‧‧First solid-liquid separation step

Step 19‧‧‧ Adjust the pH value of the spent acid solution for the first time

Step 21 ‧ ‧ cation exchange treatment of spent acid solution

Step 23‧‧‧ Adjust the pH of the spent acid solution for the second time

Step 25‧‧‧Second solid-liquid separation step to obtain fluoride

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart showing the steps of the method for treating a spent acid solution disclosed in the present invention.

The invention is directed to a method for treating a spent acid solution by recovering an acid solution after etching a wafer or glass, and treating the recovered spent acid solution to obtain a high-priced and relatively pure solution. Fluoride makes it suitable for other industrial applications. In order to thoroughly understand the present invention, Detailed steps and their composition will be set forth in the following description. However, the preferred embodiments of the present invention will be described in detail below, but the present invention may be widely practiced in other embodiments and the scope of the present invention is not limited by the detailed description. The scope of the patents that follow will prevail.

Please refer to Figure 1. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart showing the steps of the method for treating a spent acid solution disclosed in the present invention. In Figure 1, step 11 provides a spent acid solution. In the semiconductor or optoelectronic industry, etching wafers or glass, especially when etching is required to etch the solution, the etching solution is mostly an acidic solution, but the liquid recovered after etching is a waste acid solution. The waste acid solution may be hydrofluoric acid or an acid solution mixed with hydrofluoric acid, which includes fluoroantimonic acid, sulfuric acid, nitric acid, hydrochloric acid and the like.

Next, step 13 is performed to filter the spent acid solution. In step 13, whether in the semiconductor industry, the solar industry, or the panel industry, most of the materials used contain germanium or germanium dioxide, so when the wafer or glass is etched, it contains germanium impurities or Glass sand will remain in the etching solution. Therefore, in order to avoid impurities remaining in the waste acid solution and affecting the subsequent recovery of fluoride, it is necessary to first filter the waste acid solution to contain impurities or glass sand. Removed from spent acid solution.

Step 15 represents the addition of an alkaline solution to the spent acid solution to produce a spent acid solution of the fluorine-containing citrate solid. In step 15, in order to recover the valuable fluorine (F-) in the spent acid solution, the alkaline solution is first added to the waste acid solution, so that the alkaline solution reacts with the spent acid solution to form a fluoroantimonate. Solid matter. In an embodiment of the invention, the alkaline solution is a sodium hydroxide (NaOH) solution, so after the sodium hydroxide solution is added to the spent acid solution, the sodium ions in the sodium hydroxide solution and the fluorine oxime in the spent acid solution The acid reacts to form sodium fluoroantimonate (Na2SiF6), and the reaction equation is: HF _(l) + H ₂ SiF _{6 (l)} + 2 NaOH _(l) -> Na ₂ SiF _{6 (s)} + 2H ₂ O _(l) +HF _(l) (1)

Next, step 17 is the first solid-liquid separation step. Since in the foregoing step 15, the sodium fluorophthalate (Na2SiF6) formed by the reaction of the sodium hydroxide solution with the spent acid solution, and the sodium fluoroantimonate is insoluble in the waste acid solution, the centrifugation step, the dehydration step and the baking are utilized. The separation step such as a dry step separates the sodium fluoroantimonate from the spent acid solution. It is to be noted that the hydrofluoric acid (HF) in the reaction formula (1) is a mixed acid solution which still contains an acidic solution such as sulfuric acid, nitric acid and hydrochloric acid, which is still regarded as a spent acid solution.

Next, in step 19, it is indicated that the pH value of the spent acid solution is adjusted for the first time. Although in step 17, the fluorocitrate solid has been formed by adding an alkaline solution to react with fluoroantimonic acid in the spent acid solution, the hydrogen ion (H+) concentration of the spent acid solution is still high. The cation exchange resin cannot be directly used for the exchange of cations. Therefore, in the present embodiment, the first buffer is added to the waste acid solution, and the first buffer is used to adjust the pH value of the waste acid solution to make the spent acid solution. The pH value is adjusted to the first pH value, and the pH value is about 2~4. In this step, the first buffer may be a sodium hydroxide solution having a concentration ranging from 10% to 60%.

Step 21 is an ion exchange treatment of the spent acid solution. In the steps In 21, the waste acid solution is passed through an ion exchange resin, particularly a cation exchange resin, to exchange cations in the spent acid solution with cations in the cation exchange resin, thereby avoiding waste in high pH values. In an acid solution environment, cations in the waste liquid form impurities of the hydroxide salt. In an embodiment of the invention, the cation exchange resin is a sodium ion exchange resin, such that cations such as nickel (Ni), iron (Fe), aluminum (Al), chromium (Cr), etc. in the spent acid solution can be combined with The sodium ion (Na) in the sodium ion exchange resin is ion-exchanged, and the sodium ion (Na) to be utilized by the present invention is released from the sodium ion exchange resin.

Next, step 23 is performed to adjust the pH value of the spent acid solution for the second time. In the step 23, the second buffer is added to the hydrofluoric acid aqueous solution which has been subjected to ion exchange treatment, so that the pH value of the hydrofluoric acid aqueous solution is adjusted from the first pH value (the pH value is about 2 to 4) to The second pH value has a second pH value ranging from 8 to 10. In this step, the second buffer may be a sodium hydroxide solution having a concentration ranging from 10% to 60%. In addition, while adjusting the pH value of the spent acid solution, the sodium ions provided by the second buffer may be reacted with the fluoride ions in the spent acid solution to produce fluoride and an aqueous solution, and the reaction formula is as follows: NaOH _(l) +HF _(l) ->NaF _(s) +H ₂ O _(l) (2)

Then proceed to step 25. Step 25 represents performing a second solid-liquid separation step to obtain a fluoride. Since the waste acid solution is reacted with the sodium hydroxide solution as the second buffer in the step of adjusting the pH value of the spent acid solution, the reaction forms a fluoride and an aqueous solution. In order to get fluoride, The solid-liquid separation step, such as the centrifugation step, the dehydration step, and the drying step, can be used to remove the water to obtain a solid and higher purity fluoride. In the embodiment of the present invention, the fluoride is fluorinated. Sodium (NaF).

Therefore, according to the above-mentioned processing steps, it can be known that the waste acid solution can be treated in a two-stage manner, and sodium fluoride is obtained for industrial use, so that the waste acid solution in the semiconductor process has an economic value of recycling. In addition, since the fluoride is not easily dissolved in the aqueous solution, the aqueous solution can be easily removed after the above drying step, without any waste disposal cost, and the waste acid solution treatment is greatly reduced. The cost and the substantial reduction of environmental pollution caused by the waste acid solution.

Step 11‧‧‧ Provide waste acid solution

Step 13‧‧‧Filter the spent acid solution

Step 15‧‧‧ Add an alkaline solution to the spent acid solution to produce a fluorocitrate solid

Step 17‧‧‧First solid-liquid separation step

Step 19‧‧‧ Adjust the pH of the spent acid solution for the first time

Step 21‧‧‧Ion exchange treatment of spent acid solution

Step 23‧‧‧ Adjust the pH of the spent acid solution for the second time

Step 25‧‧‧Second solid-liquid separation step to obtain fluoride

Claims (10)

A waste acid solution treatment method comprising: providing a waste acid solution; performing a filtration step, filtering the waste acid solution to remove one impurity in the waste acid solution; adding an alkaline solution to the waste acid solution To produce a fluorocitrate solid; a first solid-liquid separation step, separating the fluorocitrate solid from the spent acid solution; adjusting the pH value of the spent acid solution for the first time, Adding a first buffer to the spent acid solution to adjust the pH value of the spent acid solution to a first pH value; performing a cation exchange treatment to remove at least one cationic impurity of the spent acid solution with a cation Displacement of one of the cations in the resin; second adjusting the first pH value of the spent acid solution to a second pH value, adding a second buffer to the spent acid solution to make the spent acid The pH value of the solution is adjusted from the first acid base value to the second acid base number, and the spent acid solution reacts with the buffer to produce a fluoride and an aqueous solution; and a second solid-liquid separation step is Fluoride is separated from the aqueous solution to To the fluoride solid. The method for treating a spent acid solution according to claim 1, wherein the waste acid solution comprises: hydrofluoric acid, fluoroantimonic acid, sulfuric acid, nitric acid and hydrochloric acid. The method for treating a waste acid solution according to claim 1, wherein the alkaline solution is a sodium hydroxide solution, and the concentration ranges from 10 to 60%. The method for treating a spent acid solution according to the first aspect of the invention, wherein the first solid-liquid separation step comprises a centrifugation step, a dehydration step and a drying step. The method for treating a spent acid solution as described in claim 1 further comprises adding an alkali solution to the fluoroantimonate to form fluoride and cerium oxide. The method for treating a spent acid solution according to claim 1, wherein the first buffer is a sodium hydroxide solution, and the concentration ranges from 10 to 60%. The method for treating a spent acid solution according to claim 1, wherein the first acid-base value is 2 to 4. The method for treating a spent acid solution according to claim 1, wherein the cation exchange treatment utilizes a sodium-type (Na-type) cation exchange resin. The method for treating a spent acid solution according to the first aspect of the invention, wherein the second buffer is a sodium hydroxide solution, and the concentration ranges from 10 to 60%. The method for treating a spent acid solution according to claim 1, wherein the second solid-liquid separation step comprises a centrifugation step, a dehydration step and a drying step.